1. Field of the Invention
The present invention generally relates to a power supply switching apparatus. More specifically, the present invention is directed to a circuit for switching power supplies to compact pagers, portable telephones and so on.
2. Description of the Prior Art
In recently developed/marketed portable appliances such as pagers and portable telephones, battery packs mounted to housings of these appliances are made compact in connection with the compact of the portable appliances. Conventionally, a rechargeable cell (battery), a power stabilizing circuit, and a switching circuit for switching the rechargeable cell into the power stabilizing circuit when a portable appliance is connected to an external DC power supply, are provided within a battery pack.
However, as described above, the more, the battery pack is made compact, the narrower the space capable of storing the switching circuit and the power stabilizing circuit are available. There is another problem that since heat dissipation of the power stabilizing circuit becomes large, this power stabilizing circuit may not be readily stored in such a compact battery pack. Furthermore, there is another drawback that when the switching circuit and the power stabilizing circuit would be stored within the battery pack, the number of connection terminals for connecting the battery pack with the appliance housing should become large.